First, a word about cholesterol. The only way I can tell that I am limiting dietary cholesterol is that I never get to eat eggs, liver, or shrimp. The research clearly shows that avoiding dietary cholesterol has absolutely nothing to do with avoiding any disease. And getting a half gram of daily choline becomes nearly impossible. So my personal opinion is that promoting limits on dietary cholesterol is a political gimmick to get the naive to breakfast on over-priced carbohydrates, whose nutritional poverty always seems to require that ground-up vitamins and minerals be mixed in. Vitamins and minerals don't need to be added to an egg to make it a valuable food.
The main division of the non-essential fats in a nutrition program is between saturated fat and monounsaturated fat. When you first look at food composition tables, you may be surprised that a demonized food such as bacon actually has more "heart healthy" monounsaturated fat than "artery clogging" saturated fat.
There is a scientific reason why this division between saturated and monounsaturated fat is too simplistic. Fatty acids in food come three-at-a-time as triglycerides, and plants and animals put the fatty acids in different positions on the molecule, so that a particular fatty acid in a particular position may not be functional in a particular way. Also, individual fatty acids, while they are easy to categorize as saturated or monounsaturated, have not been studied in sufficient detail to truly understand their possible functions. For instance, many of the shorter-chain saturated fatty acids present in milk fat do not raise serum cholesterol and exhibit anti-microbial activity.
There is also a basic decision to be made whether adverse effects from saturated fat are ultimately caused by too much carbohydrate. Most studies of the deleterious effects of fat have been done in the presence of high carbohydrate. When blood sugar has to be lowered after a meal but the body's carbohydrate reservoirs are full, there is nowhere to put the sugar so the body has to either change the sugar to fat or at least promote fat storage. When this is happening, dietary intake of some of the saturated fatty acids can be especially detrimental since saturated fat is what the body is synthesizing from the excessive carbohydrate, and the liver has to make lots of cholesterol to ferry all this fat to the storage depot. When eating low-carb though, the body uses saturated fat for fuel rather than storage, and probably uses dietary cholesterol to produce more beneficial HDL cholesterol.
So in my personal experimentation, rather than focusing on the numbers for saturated and monounsaturated fat, I compared three groups of dietary fat sources with significant differences in fatty acid composition that were major components of my diet. I attempted to maximize intake of one group while minimizing intake of the other two to see if I could tell the difference:
My personal experience was that the highly-touted choice 1 above just made me totally lose interest in the experiment. My body didn't like it, and wasn't going to eat that way! When I added animal fat back in, my interest picked up again. If you're a man, minimizing testosterone by avoiding animal fat is not a good strategy.
If I was eating low-carb with milk fat approaching 10% of calories, milk fat increased my appetite, lowered my energy level, and made me gain weight, all symptoms of insulin resistance. This is the fat I lowered if I gained weight or got too hungry on low carb, and it caused the same problems as too much carbohydrate, including inflammation. Milk fat at fairly low levels also interfered with the dopamine-enhancing and insulin-sensitizing effects of chromium, as well as producing a rheumatoid arthritis-like effect in an elbow joint, so regretfully I had to eliminate it altogether. One fatty acid that distinguishes milk fat from other saturated fats is a high level of Myristic Acid (14:0), so I tried to maximize this fatty acid without using milk fat, and indeed, I saw a weaker version of this same insulin resistance effect. I could not get this effect from highly-saturated fats that are low in 14:0 such as cocoa butter and palm oil. The bottom line is that when I eat according to appetite and include milk fat, cheese, butter, etc., then my calorie intake increases by 15%, and even severe carbohydrate restriction does not solve the problem.